The present invention relates to a switch device which comprises a frame; an electric switch which is installed in the frame and can be pressed into a connecting position and will return to an initial position when the pressure ceases; and a switch-actuating plunger which is made up of a pressing knob and a spring part. Upon being pressed, plunger brings the switch into the connecting position and, upon the termination of the pressure, allows it to return to the initial position.
The applications of the invention include electrically operating apparatuses which comprise a peripheral device, wherein the operating state of the electric system depends on the peripheral device being in place. In order to operate, such apparatuses require a switch device equipped with a plunger which the peripheral device presses upon when in place and which is released and returns to its initial position immediately when the peripheral device is lifted off. One example of the said apparatuses is the telephone, in which the cradle of the handset may be equipped with a plunger acting on a moving switch. The handset, when on the cradle, presses this plunger, thus keeping the switch in the connecting position. When the handset is lifted the plunger is released and at the same time releases the switch into its initial position. These functions of the switch device pressed by the handset are necessary for the appropriate operation of the telephone.
A moving switch may be equipped with a separate, spring-loaded plunger when it is desired to prevent the pressing force from acting as such directly on the switch. The switch may be prone to damage or wear, in which case the plunger protects it receiving a portion of the pressing force and by attenuating the impact caused by it and aimed at the switch. On the other hand, it is possible that the presence of the plunger in the switch construction is purely a question of design and dimensioning. The actual switch may be located so that it is impossible to press it directly, in which case a separate plunger is necessary for directing an impulse to the switch from pressure applied elsewhere.
In one prior-art switch system used in telephones, the plunger with its pressing knob is fitted in an opening in the cradle of the handset and is connected by means of a lever spring to a microswitch under the cradle. The end of the lever spring is, in this case, articulated to the switch frame and is arranged to press a moving switch part connected to the frame. This system has, however, the drawback that the lever spring is unreliable in operation and thus is insufficient when acting alone. Therefore, it has been necessary to provide as an aid for it an additional spring, for example located in parallel with the pressing knob, directly under the plunger. However, the additional spring makes the construction more complicated and more space-consuming.